U pipe solar collector How it works: 1) Connect with pressure water tank and work station. Water is circulated through the header via intermittent pump cycling. Each time the water circulates through the header, the temperatures is raised by 5-10C. Throughout the day, the water in the tank is gradually heated. 2) Solar absorption: Solar radiation is absorbed by the solar tubes and converted into heat. 3) Solar heat transfer: Heat pipes conduct the heat from within the solar tube up to the U pipe.